This invention relates generally to expandable fasteners and more particularly, it relates to an improved insert moldable ratchet rivet assembly for securing a plurality of panels together which includes a drive-pin insert of a unique construction to facilitate the pull-up operation with a reduced amount of force and to form slots in the shank of a rivet housing.
There are known heretofore in the prior art various types of such expandable fasteners. For example, U.S. Pat. No. 4,377,358 to Burnell J. Wollar issued on Mar. 22, 1983, discloses a one-piece plastic fastener 10 for lockable engagement in an opening in a panel which includes a stem 12 and a pair of arms 18 and 20 connected to and swingable about an inner end of the stem. A head portion is integrally formed at a free end of each of the arms, and these two head portions 32 and 34 are swingable with the arms to come together to define an apertured head 36 having an orifice 38 that embraces the stem 12. The stem and arm are driveable into the opening in the panel to locate the head against an outer side of the panel. The stem 12 is shiftable through the orifice 38 towards its inner end and causes the arms 18 and 20 to swing transversely and bear against the inside wall of the panel. Serrations 48 are provided between the head 36 and the stem 12 to maintain the fastener in lockable engagement with the panel.
In U.S. Pat. No. 4,403,893 to Burnell J. Wollar issued on Sep. 13, 1983, there is disclosed a one-piece plastic fastener 10 for lockable engagement in a workpiece opening which includes a stem 12 having an outer end 16 and an inner end 14 from which a pair of integrally formed arms 18 and 20 extend. The arms have two ends, one end forming an acute angle with the inner end 14 of the stem 12, and the other end terminating at an integrally formed head portion. The head portions 26 and 28 are swingable with their respective arms about the inner end 14 of the stem to cooperatively engage each other and to form a complete head 30 having an orifice 32 embracing the stem 12. The stem and arms are insertable into the opening 42 to locate the head against the outer side of the workpiece. Positive and outward withdrawal of the stem 12 through the opening and the orifice causes the arms to swing laterally and abut firmly against the inner side of the workpiece. Serrations 50 disposed between the head and the stem maintain the fastener in lockable engagement with the panel by readily permitting outward movement of the stem while resisting its inward movement.
Further, U.S. Pat. No. 4,556,351 to Burnell J. Wollar and Richard J. Schwind issued on Dec. 3, 1985, teaches an expansion rivet assembly 10 which is comprised of two separately molded plastic components, namely: (1) an expandable hollow plastic rivet or female member 20 and (2) a plastic drive-pin or male member 22. The rivet has a head 26 and a shank 24 which is insertable in aligned holes in workpieces to be joined. The drive-pin has a head 42 and a shank 40 which is inserted in the rivet bore 28 and adapted to be axially drawn into the bore by a tool which causes the pin head 42 to engage the insertion end of the rivet shank and effect outward expansion of the rivet shank wall 36. This axial movement also results in the breaking off of the projecting end 48 of the pin shank 40 at a break-away indentation 46 formed in the pin shank.
However, none of the prior art discussed above teach an insert moldable ratchet rivet assembly of a unitary construction for securing a plurality of panels together like that of the present invention which includes a drive-pin insert of a unique configuration to facilitate outward expansion of the rivet shank walls portions with a reduced pull-up force and to form slots in the shank of a rivet housing. The drive-pin insert includes a first end portion, second end portion, and a body portion extending between the first and second end portions. The body portion has a plurality of segments which are spaced apart from each other to form recessed flattened surfaces therebetween. Each of the flattened surfaces is provided with a plurality of lengthwise-spaced horizontal teeth which produces a line contact hinge with respect to corresponding lateral teeth formed in the shank wall portions of the rivet housing. As a result, the outward flexing of the rivet shank wall portions is thereby facilitated.